Deciphering the role of polyphenol in defence mechanism against tea mosquito bug (Helopeltis theivora Waterhouse.) in cocoa (Theobroma cocoa L.)

Tea mosquito bug (TMB) is a serious pest of cocoa whose prevalence is high, mostly during summer and post monsoon season. Three species of tea mosquito bug have been reported on cocoa: Helopeltis antonii Signoret, H. theivora Waterhouse, and H. bradyi Waterhouse. H. theivora is the most prevalent one causing damage to young shoots, cherelles and pods. Rearing of tea mosquito bug on cocoa was found to be a failure in the present study hence Helopeltis theivora Waterhouse was maintained on the alternate host mile-a-minute (Mikania micrantha Kunth) under laboratory condition in insect rearing cages. Using freshly reared tea mosquito bugs twenty cocoa hybrids were screened for resistance and were ranked after 72 hours of screening. All the hybrids having less than three lesions per plant in seedlings and less than 33 lesions on pods were ranked as highly resistant. It was observed that hybrids classified as highly resistant had significantly higher phenol content than those classified as susceptible. The significantly low phenol content in the susceptible hybrids suggests that phenolics have a function in mediating resistance to tea mosquito bug in cocoa. From correlation and regression analysis it is confirmed that phenol content can be used as a potential marker indicating the level of resistance of cocoa hybrids against tea mosquito bug resistance.

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• If neither of these applies but you are able to provide details of access elsewhere, with or without limitations, please do so. hours. Attempt to rare it on cocoa seedlings was a failure due to lack of oviposition in cocoa.

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The alternate host mile-a-minute (Mikania micrantha) was utilised to combat the problem. [7] 70 developed a standard procedure for this purpose, which was followed. Newly reared insects 71 collected from the raring cage were used for further screening procedure.

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Screening of tea mosquito bug on cocoa seedlings 73 Patch budding was done on six-month-old root stock to raise the screening materials. Medium matured, newly picked pods of each genotype were used for pod screening.

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Detached pods in insect rearing cages were subjected to artificial screening. Helopeltis theivora 84 Waterhouse was released to freshly collected pods at the rate of 4 per cage (2 adult male and 2 85 adult female). The number of feeding lesions was counted at 12 hour intervals until 72 hours, 86 and the infestation was assessed [8] (Fig 2).  for 20 minutes at 10,000 rpm. The supernatant was then poured into an evaporating dish. To 99 collect all of the phenol present in the sample, this method was repeated for 2-3 times.

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Evaporating dishes were placed in a hot water bath for one hour to eliminate surplus ethanol.

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Evaporating dishes were placed in a hot water bath for one hour to eliminate surplus ethanol.

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To the left-over residue 40 mL of distilled water was added. From that 0.2 mL aliquot was 103 taken to a test tube and 13 mL distilled water was added followed by, addition of 0.5 mL FC 104 reagent. The reaction mixture in the test tubes was incubated for 3 minutes. After that, a 2 mL 105 solution of 20 percent Na2CO3 was added. These test tubes were placed in a boiling water bath 106 for one minute before being incubated at room temperature for 60 minutes. The absorbance 107 was measured at 650 nm using a spectrophotometer against a reagent blank. Total phenols were The tea mosquito bug (Helopeltis theivora Waterhouse) is a major sucking pest that attacks 121 young shoots, cherelles, and mature pods of cocoa. Twenty cocoa hybrids were chosen for tea 122 mosquito insect screening in this study based on their general vigour and yield performance.

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The field was surrounded on three sides by old germplasm blocks and on one side by a cashew 124 plantation. When compared to the neighboring fields, natural infestation was surprisingly low 125 in these hybrids.

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Tea mosquito bug is a polyphagous pest with a wide range of hosts including many  Pearson's correlation analysis was carried out to determine if there was a link between 179 polyphenol content and tea mosquito bug attack, and it was discovered that total phenol content 180 in both pod husk and shoot was inversely related to TMB attack, with a high significant 181 negative correlation of 0.431 and 0.518, respectively ( Fig. 1 and Fig. 2).  The study clearly indicated that polyphenol content in cocoa has a great influence on 206 conferring resistance against tea mosquito bug in cocoa and can serve as a selection criteria for 207 identifying cocoa genotypes with tea mosquito bug resistance. Even though this is a 208 preliminary study, it represents a good step toward understanding the tea mosquito bug 209 resistance mechanism in cocoa and will be a foundation for future researches on this topic. All 210 the genotypes identified with resistance were used as parental material in establishing 211 polyclonal garden. Planting material from this garden supplied to farmers will ensure tea 212 mosquito bug resistance to certain extent. 213